1.7. CONCLUDING REMARKS

In summary, at a resolution of typically a few tens to a few hundred
parsecs,
the local disk galaxy population appears to host bulges that more and more
resemble disks, and disks that more and more resemble bulges. Disks may be
denser than exponential, and bulges may be less steep than de Vaucoluleur's
structures. Bulges are claimed to have the kinematics of thickened
disks, and
buckled bars can be as dynamically hot as the structures claimed to be
"true" bulges. The average stellar population properties (i.e., stellar
ages and metallicities) remain the only surviving distinction between
"massive" and "small" bulges and, more generally, between massive bulges
and the centers of disks. This could certainly be an indication of different
formation processes, but could also be the result of similar processes
occurring at different epochs in the Universe (and thus naturally
generating a positive correlation between stellar densities and
ages). In my view, what is needed at this point is a shift of the debate
from the arena of morphological classifications, where bulges and disks
are distinct entities and the question
"what is the origin of bulges" is kept distinct from the question "what is
the origin of disks," to one where disk galaxies are studied as a whole
without the constraints of a rigid classification scheme. The historical
focus on morphology, while highlighting many details in the trees, may
in fact have
hidden the true nature of the forest. The expected outcome will be a renewed
concept of the "Hubble sequence" that will be ultimately be based on
physical rather than morphological considerations. Clarifying what we really
see nearby as the endpoint of the galaxy evolution process is essential in
order to meaningfully answer how the distant progenitors, which are seen in
the most remote regions of the Universe, transform themselves to become the
descendants that populate our own surroundings.

Acknowledgements.
I thank L. Ho for the invitation to this very stimulating meeting, and
especially for his patience waiting for this manuscript. I am grateful to my
collaborators, V. Debattista, L. Mayer and B. Moore for kindly making
available some of our results prior to publication. Many thanks to F.
van den Bosch and S. Lilly for comments on a previous version of this
manuscript.